Resin containers, typical examples of which are polypropylene (PP) bottles and polyethylene terephthalate (PET) bottles, are used to hold a variety of liquids, such as a beverage, a cosmetic product, a pharmaceutical product, a detergent, and a toiletry including shampoo, as the content liquids. Such a container is generally produced by blow molding a preform that has been formed by a thermoplastic resin material as mentioned above.
As an example of blow molding in which a pressurizing medium is supplied into a preform to mold the preform into a container of a shape conforming to an inner surface of a cavity of s blow molding mold, liquid blow molding in which a liquid is used as a pressurizing medium is known.
Further, as described in PTL1, for example, a container production method is known in which, during liquid blow molding, as a pressurizing medium, a content liquid to be held in a container is supplied to a preform when a container is produced. Thus a step of filling a content liquid into a molded container is omitted, and a production step and molding and filling lines can be simplified.